Saturday, June 13, 2009

Orthetrum chrysis ; Larva Emergence

Although dragonfly larvae have been studied widely, this aspect of their life history still harbours unsolved mysteries. For example, there’s several dragonfly genus whose larvae are still unknown and not found or described. The best way to study larvae ecology is to rear them ex-situ. This requires patience, time and acquired knowledge through practice. Inspired by the excellent work by Dr. Ian Choong from Malaysia and encouragement from Yeh Wen-Chi in Taiwan, I decided to take on this challenge whole heartedly.

Two to three days prior to emergence, a typical larva will stop feeding and climb partially out of the water. This is when aquatic respiration slowly change into atmospheric respiration. Once ready it will leave the watery environment into an aerial existence. After rearing this larva for 20 days, a miracle of nature finally unfolded.

Tropical dragonflies mostly emerge at night to pre-dawn. There are four stages of emergence. The first is when the larva search for a suitable support, climbing upwards and away from water. At this stage, the cuticle is still intact.

At second stage. the cuticle of the head and thorax split with the adult now pushing itself out of the moult (known as exuvia in dragonflies). Looking at the process, I actually sensed the dragonfly’s physical exertion. Slowly, the head, thorax and legs emerged with only the abdomen still inside the exuvia. Normally, a dragonfly would then rest for a while.
When it has regained energy, it swung forward to hang onto the exuvia and pulled its abdomen out. This is the third stage. The dragonfly is now fully emerged but looks all wriggled and fragile.

Finally in stage four, bodily fluids are pumped throughout the body to expand the abdomen and wings and also gaining full colour. Just like an ugly duckling, its wings open and transformed into a beautiful reddish female Orthetrum chrysis.
The entire four stages require 1-2 hours. Sacrificing sleep from 4-6am to witness this event is certainly worth it. For a dragonfly, it now enters an aerial lifestyle of hunting, territorial fights and procreating the next generation.

Orthetrum chrysis is a common dragonfly. Although mostly encountered at forest margins, we can also find them in well-vegetated park ponds. Of the several red-coloured dragonflies in Singapore, males of O. chrysis can be recognised by its red abdomen and blackish-brown thorax.


Pictures taken at: ex-situ, May 2009 (larva and emergence); Bishan Park pond, September 2008 (adult male).


References:

Corbet, P. S. & S. J. Brooks, 2008. Dragonflies. HarperCollins Publishers, London, UK.

Silsby, J., 2001. Dragonflies of the World, CSIRO Publishing, Victoria, Australia
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7 comments:

Randy Emmitt said...

Great article! I have witnessed at least 4 different species emerge through the entire process. Luckily the ones I have witnessed emerged after 11PM so I just had to stay up late.

ria said...

WOW, this is so cool! Amazing to watch this in the photos that you worked so hard for. Thank you for sharing!

Federick Ho said...

Wow, first time seeing this. Very good capture. Thanks for sharing.

C.Y. Choong said...

You are learning fast..... well done mate!

I give you a tip how to take emerging dragonfly with self control background.....

try to rear the larva in a small plastic container and put a stick (not log.... hehhehe) in the container. Put the container (with the stick) in a bigger container and make sure that the lid of the bigger container doesn't touch the tip/end of the stick (so that larva may not be able to climb up to the lid of the bigger container).

upon mature, the larva will climb up to the stick. When the larva starts to emerge, you may take out the small container and put it at a place with desired background. Then you emerging larva photos will have nice backgroud.

good luck.

Ian

matinggeckos said...

Thanks everyone.

Watching the larva emerged was like watching a child growing into adult..

Thanks Ian. I'll try your tip.

Cheers
Robin

Dragonchaser said...

Amazing photos and very educational post, I must try this sometimes!

I'm afraid I still haven't seen an emergence from start to finish, I had only come across a few emergences when they were already in the late stages.

Thanks for sharing.

rocksea said...

wow, worth spending the time awake, you captured the dragonfly coming out, so nicely :)

came here searching for the jumping spider.